A system-dependent tractive force interruption takes place when shifting gears in automatic multi-speed drives. Normally the following processes take place when shifting a gear:                reduction of the torque transferred from the drive motor        engaging of the separating clutch        release of the old gear        engagement of the new gear        disengaging of the separating clutch        increase of the transferred torque by an amount that corresponds to the appropriate pedal position.        
Shifting should take place quickly especially in the case of high tractive power requirements, such as in inclinations in order to avoid a slow-down of the vehicle during shifting. In addition, comfort criteria must be maintained and the load of the shift elements must remain within certain limits. Depending on the driving situation, a different time sequence is necessary for the process steps, so that the shift period, comfort, and load criteria can be maintained.
DE 198 02 736 A1 discloses a method where the speed of the torque decrease at the start of the shifting process and of the torque increase at the end of the shifting process is determined depending on the vehicle acceleration and the gas pedal angle. According to this known method, the clutch is engaged and the gear is released at the end of the ramp with which the torque is reduced. In certain driving situations, the timing for engaging the clutch is too early or too late compared with an optimal shifting operation.
The present invention is based on the task of developing a method for controlling the gear release where the time sequence of the process steps while releasing the gear can be optimized in a simple fashion.
This problem is solved according to the inventive method. Accordingly, the steps—application of a shift load for decoupling the shift elements and opening the separating clutch—are triggered at that point when the vehicle acceleration, which is continuously determined at each program step, reaches an assigned vehicle acceleration value. During the start of the shifting process the current initial acceleration of the vehicle is determined and stored in the memory of the electronic control system. Then the torque of the drive motor is continuously reduced by lowering the injected fuel quantity supplied by the fuel injection pump. At the beginning of the shift, a first and second vehicle acceleration value is determined dependent on the starting acceleration of the vehicle, the injected fuel quantity that is supplied to the drive motor and the engaged gear. The current vehicle acceleration is constantly compared with the first and the second vehicle acceleration values. As soon as the current vehicle acceleration reaches or falls below the first vehicle acceleration value, the actuator is applied with a shift power for the shift elements to be decoupled, so that consequently the gear is released.